Pump



March 16, 1948. J. H. cox Erm.

PUMP

Filed Nov. \8,' 1944 ON 0 0 0 H 0 O O O 0 O O O INVENTOR Joseph/7i 60x, Herbe/1A! /Pase and ayag CoM/aco.

`ATTORNEY Patented Mar. 16, 1948 2,437,849 FICE PUMP Joseph n. cox, Pittsburgh, August r.

Herbert A. Rose, Pittsburgh, menne assignments, to the America, as Atomic Energy Commission Wilkinsburg, and Pa., assigner-s, by United States of the United States Colaiaco,

represented by Application November 8, 1944, Serial No. 562,518 7 Claims. (Cl. 23o-101) Our invention relates to a pump and. particularly, to a high elciency multistage pump of the diffusion type.

In the operation of vapor diiluslon pumps it has heretofore been customary to collect the condensate from the various pump stages and return the condensate as a whole to the preliminary or high vacuum pumping stage of the pump. This return of all of the condensate to a single portion in the boiler produces a cool spot which reduces the efficiency of the pump by preventing evaporation from a portion of the surfaces of the liquid in the boiler. Also, since the various stages of the pump are at different was heretofore found desirable to use to prevent back diilusion between stages of the pump.

In a pump according to our invention, the various pump stages are connected to various boiler .iets and the condensate from the various stages is returned to the boiler compartment from which it came. The return connections are extended below the surface of the liquid in the boilers so that it is unnecessary to use a liquid trap to prevent vapor passing through the condensate return connection, To further. eliminate cold spots in the boiler, preliminary heating devices are connected to preheat the condensate before returning it to the boiler chambers. While the condensate from all stages may be preheated as desired, we have found that the condensate from the preliminary stage is of such small quantity that it does not produce an appreciable cold spot in the boiler and may be returned to the associated boiler compartment.

It is an object of our invention to provide a. high eiciency diusion pump.

lt is a further object of our invention to provide a diffusion pump in which the condensate is returned to the boiler compartment from which it originated.

It is a further object of our invention to provide a condensate return which does not require liquid traps.

It is a further object of our invention to provide preheating means for the condensate returned to the boiler.

It is a further object of our invention to elimi nate cold spots in the pumping boilers.

It is a further object of our invention to provide a pump boiler in which there is substantially uniform evolution of vapor over the entire liquid surface.

It is a further vide a pump which is operable against higher back pressures.

Other objects and will be apparent from scription taken in conjunction panying drawing, in which:

liquid traps" the various advantages of oui invention the following detailed dewith the accompressures, ity" object of our invention to proa heating element il is Figure 1 is a sectional elevation of a two-stage the condensing chamber i drawing the non-condensive gas through an intake pipe 8 and forcing them into the upper part of the condensing chamber 1. The condensate from the first pumping stage 2 collects in the bottom of the condensing chamber i and returns through a condensate-return connection 9 to a point below the surface of the liquid in the boiler 4, so that the differential of pressure between the boiler and the pumping stage will produce an elevation of liquid in the return connection s and eliminate the passage of vapor or gas between the boiler 4 and the rst condensing chamber l,

The second pumping stage 3 operates against a relatively higher back pressure and consequently requires a larger amount of vapor at a higher pressure and is, therefore, connected to a boiler compartment 5 having a large evolution area. The second pumping stage 3 also is provided with a condensing chamber l0 which also includes a cooled baille II largely to prevent direct-flow of the pump vapor into the exhaust passage I2. The condensate from the second stage 3 is collected in -'a trough-like member I3 secured to the wall of the pump and passes I4 to a point below l through a return connection the surface of the liquid in the boiler compartment 5 from which it originated. By returning the condensed vapor directly to the boiler compartment from which they originated, it is possible to use pump fluids of different volatility in the respective pumping stages. Also since there is no return connection between the boiler com partments, the boiler compartments li and 5 may operate at different pressures as may be best to secure the maximum efllclency in the pump.

In order to prevent the returning condensate from producing a cool spot in the boiler chamber. applied to the return connection Il, any suitable heat element I5 may be utilized, but we have found it convenient to provide a. coil-like pipe I6 in the return connection I4 and to apply an electric heater I5 about this portion I6 of the return connection.

Instead of applying an auxiliary heater to the return connection I4, the return connection I4 may be made through a heated portion I8 of the boiler Wall such as the bottom plate I1 and thereby be preheated before emerging into the boiler compartments.

While we have shown our auxiliary heater I8 or I8 as applied only to the secondary stages of the pump, it is apparent that this preheater I6 or I8, may, if desired, be applied to the preliminary stage 2 as well, although we have discovered that the small quantity of vapor condensed in the preliminary stage 2 does not have a particularly deleterious influence on the boiler 4 of that stage. While for simplicity of illustration we have shown and described our invention as applied to the soealled up-draft pump, it will be quite apparent that the invention is applicable to other types of pumps either of a lateral or down draft variety.

It will be apparent that changes and modifications can be made without departing from the true spirit of our invention.

We claim as our invention:

1. A multistage diiusion pump comprising a boiler compartment for each pump stage, a condensing chamber for each pump stage, a separate condensate return from each condensing chamber to the respective boiler chamber and heating means associated with one of said condensate returns.

2. A multistage diffusion pump comprising a boiler compartment for each pump stage, a condensing chamber for each pump stage, a separate condensate return from each condensing chamber tothe respective boiler chamber, and means associated with one of said returns for preheating Y the condensate before returning it to the boiler.

. ,3. A vapor diusion pump comprising a plurality of pumping stages, a boiler compartment for each pumping stage, separate condensing chambers fOr each Dumping stage, a return connection for returning condensate from each section to the associated boiler compartment, said return connections terminating below the surface of the liquid level in the boiler, and heating means assoelated with one of said return connections.

4. A vapor diffusion pump comprising a plurality of pumping stages, a boiler compartment for each pumping stage, separate condensing chambers for each pumping stage, a return connection for returning condensate from each section to the associated boiler compartment, said return connections terminating below the surface of the liquid level in the boiler, and a heating element applied to the return connection of the high pressure stage.

5. A vapor diffusion pump comprising a plurality of pumping stages, a boiler compartment for each pumping stage, separate condensing chambers for each pumping stage, a return connection for returning condensate from each section to the associated boiler compartment, said return connections terminating below the surface of the liquid level in the boiler, a portion of the return connection of the high pressure stage being embedded in a heated portion of the boiler chamber.

6. An oil diffusion pump comprising a plurality of pumping stages, a boiler compartment for each pumping stage, a condensing area for each pumping stage, means for collecting the condensate for each pumping stage, independent oil returns from each pumping stage to its respective boiler compartment, and heating means associated with one of said oil returns.

'7. An oil diffusion pump comprising a plurality of pumping stages, a boiler compartment for each pumping stage, a condensing area for each pumping stage, means for collecting the condensate for each pumping stage and independent oil returns from each pumping stage to its respective boiler compartment, and means for preventing.

the returning oil from producing cold spots in the boiler.

JOSEPH H. COX. AUGUST P. COLAIACO. HERBERT A. ROSE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,080,421 Hickman May 18, 1937 2,153,189 Hickman Apr. 4, 1939 

